As director of the movie Josh Boone recently revealed to Slash Film, The New Mutants was originally intended to be much more closely aligned to the X-Men timeline, featuring Storm in a central role.
Through it’s long and troubled production, The New Mutants has gone from being an off-shoot of the live-action X-Men movies to becoming its own separate franchise.
Perhaps being free of the baggage that comes with the X-Men franchise will allow The New Mutants to stand on its own.
They really pushed us to keep it separate from X-Men stuff, even though it’s set in the X-Men universe.